For the purposes of fuel efficiency improvement, exhaust emission reduction and the like, some automobiles having an internal combustion engine and the like as an engine may be provided with the so-called idling stop or economy running function (which will be hereinafter simply referred to as “eco-run”) of automatically stopping the engine in the state where the vehicle stops and the driver operates a brake pedal and also automatically restarting the engine by the driver's operation for restarting the vehicle, for example, by decreasing the operated amount of the brake pedal to the level of zero.
Furthermore, there is also a starter for starting the engine in which an engagement mechanism for engaging the pinion gear of the starter with the ring gear of the engine and a motor for rotating the pinion gear can be separately driven. In addition, when starting the engine, such an approach may be employed that the engine is cranked by the motor after the pinion gear is engaged with the ring gear.
In the case where such a starter is used to start the engine, when automatically restarting the engine as described above, the control device controls the driving signals for the above-described pinion gear and motor to be output at an appropriate timing. However, when first starting the engine from the state where the vehicle stops, the output voltage of the battery is lowered, for example, due to deterioration, temperature decrease and the like, which may prevent the control device from being activated. This may cause a situation where the engine cannot be appropriately started.
For solving the above-described problem, Japanese Patent Laying-Open No. 2010-090874 (PTL 1) discloses a configuration in which, when starting the engine by an ignition key, an engagement mechanism is driven by a start request signal caused by the ignition key to perform an engagement operation with the pinion gear while driving the motor by using a signal obtained by delaying this start request signal in the delay circuit.